Prior devices for receiving, inspecting and storing instruments such as bank notes have comparatively low security standard. Such devices have a housing which consists essentially of ordinary steel sheet and is closed with ordinary security locks. It is not especially difficult to procure suitable duplicate keys for opening the housing. The housing cannot withstand serious efforts to reach the instrument receptacle and/or the inspection means by force. Such a unit is therefore unfit for use at customer-operated facilities in banks, let alone outside of a bank building, at least according to the security standards deemed acceptable in the Federal Republic of Germany.
Of course, it has long been possible for bank customers to deposit money at the bank outside of office hours by dropping the money off in a locked container, generally through an opening in the outside wall of the bank building. The container can be opened the next day and the cash can be verified, sorted, counted and credited from a slip enclosed in the container. One difficulty with existing devices for receiving, inspecting and storing instruments is that once the bank notes have been stored in the instrument receptacles, they can no longer be traced to a particular person. The bank notes must be reliably checked before they are deposited in the receptacles, and immediately returned to the customer if there are any doubts as to their genuineness or other defects. Hence, it is not sufficient simply to provide a deposit slot in the housing, which might in particular consist of a thick-walled vault; a suitable conveyor mechanism must also be provided, and a sufficiently large dispensing opening so that rejected bills can be returned to the customer. The wall openings required for a deposit pocket in which a bundle of bank notes may be deposited and a return pocket from which a bundle of bank notes may be returned, however, are too large for a vault, and hence unacceptable. Hence, the security arrangements required for keeping bank notes could not be met by simply reinforcing the housing in the known devices.